Self-Deception and it's causes

There are so many people in this world that seem to be a certain thing; however, upon further introspection, we find that many of these people hide things and usually hide things from themselves as well (i.e. Theists). I've been doing a lot of thinking and reading, and have come to the conclusion that it involves the use of the commitment and consistency principle in psychology, which goes something like this: "Whenever we prescribe to a certain array of behaviors, there is a drive to remain consistent. the reason for this stems from society; people that are considered inconsistent are associated with mental illness." (excerpt from Influence: The Psychology of Persuasion (by Richard Cialdini, Ph.D.)). From my perspective, it seems like people erect these barriers of self-deception because of simply our innate tendency to make things simpler and to NOT THINK. Any other thoughts??